Conductive laminate and manufacturing method of conductive laminate

ABSTRACT

Provided is a conductive laminate including a base material and a conductive ink film provided on the base material, in which a region that extends from a first main surface toward a second main surface to a position being away from the first main surface by a distance equivalent to 50% of a thickness of the conductive ink film has a first void ratio of 15% to 50%, a region that extends from a position being away from the second main surface toward the first main surface by a distance equivalent to 10% of the thickness of the conductive ink film to the second main surface has a second void ratio which is smaller than the first void ratio, and the conductive ink film comprises at least one metal selected from the group consisting of silver, gold, platinum, nickel, palladium, and copper.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of International Application No.PCT/JP2021/035589, filed Sep. 28, 2021, which claims priority toJapanese Patent Application No. 2020-165595 filed Sep. 30, 2020. Each ofthe above applications is hereby expressly incorporated by reference, inits entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a conductive laminate and amanufacturing method of the conductive laminate.

2. Description of the Related Art

A conductive laminate composed of a base material and a conductive filmprovided on the base material is used as an electronic material formanufacturing various electronic devices.

For example, JP2010-183082A describes a substrate including a basematerial and a conductive pattern that is provided on the base materialand contains conductive inorganic metal particles and an organic metalcomplex providing a conductive channel between at least some of theconductive inorganic metal particles.

SUMMARY OF THE INVENTION

In some cases, a conductive laminate is required to satisfy both the lowsurface resistivity and thermal cycle stability.

The present disclosure has been made in consideration of the abovecircumstances. According to an embodiment of the present invention,there are provided a conductive laminate having a low surfaceresistivity and excellent thermal cycle stability and a manufacturingmethod of the conductive laminate.

The present disclosure includes the following aspects.

<1> A conductive laminate comprising a base material and a conductiveink film provided on the base material, in which in a case where asurface of the conductive ink film close to the base material is definedas a first main surface, and a surface of the conductive ink film farfrom the base material is defined as a second main surface, a first voidratio in a region that extends from the first main surface toward thesecond main surface to a position being away from the first main surfaceby a distance equivalent to 50% of a thickness of the conductive inkfilm is 15% to 50%, and a second void ratio in a region that extendsfrom a position being away from the second main surface toward the firstmain surface by a distance equivalent to 10% of the thickness of theconductive ink film to the second main surface is lower than the firstvoid ratio.

<2> The conductive laminate described in <1>, in which the first voidratio is 30% to 40%.

<3> The conductive laminate described in <1> or <2>, in which the secondvoid ratio is 20% or less.

<4> The conductive laminate described in any one of <1> to <3>, in whichthe conductive ink film contains at least one metal selected from thegroup consisting of silver, gold, platinum, nickel, palladium, andcopper.

<5> The conductive laminate described in any one of <1> to <4>, in whichthe conductive ink film has a thickness of 0.5 μm to 30 μm.

<6> A manufacturing method of the conductive laminate described in anyone of <1> to <5>, the manufacturing method including a step of applyinga first conductive ink containing metal particles onto a base material,a step of baking the first conductive ink, a step of applying a secondconductive ink containing a metal salt or a metal complex onto the bakedfirst conductive ink, and a step of baking the second conductive ink.

<7> The manufacturing method of the conductive laminate described in<6>, in which the metal particles are particles containing at least onemetal selected from the group consisting of silver, gold, platinum,nickel, palladium, and copper.

<8> The manufacturing method of the conductive laminate described in <6>or <7>, in which the metal particles have an average particle diameterof 10 nm to 200 nm.

<9> The manufacturing method of the conductive laminate described in anyone of <6> to <8>, in which a content of the metal particles is 10% bymass to 90% by mass with respect to a total amount of the firstconductive ink.

<10> The manufacturing method of the conductive laminate described inany one of <6> to <9>, in which each of the metal salt and the metalcomplex contains at least one metal selected from the group consistingof silver, gold, platinum, nickel, palladium, and copper.

<11> The manufacturing method of the conductive laminate described inany one of <6> to <10>, in which the metal complex is a metal complexhaving a structure derived from at least one compound selected from thegroup consisting of an ammonium carbamate-based compound, an ammoniumcarbonate-based compound, an alkylamine, and a carboxylic acid having 8to 20 carbon atoms, and the metal salt is a metal carboxylate having 8to 20 carbon atoms.

<12> The manufacturing method of the conductive laminate described inany one of <6> to <11>, in which a content of each of the metal salt andthe metal complex is 10% by mass to 90% by mass with respect to a totalamount of the second conductive ink.

<13> The manufacturing method of the conductive laminate described inany one of <6> to <12>, in which the first conductive ink is appliedusing an ink jet recording method in the step of applying a firstconductive ink, and the second conductive ink is applied using an inkjet recording method in the step of applying a second conductive ink.

<14> The manufacturing method of the conductive laminate described inany one of <6> to <13>, in which at the time of applying the firstconductive ink in the step of applying a first conductive ink, atemperature of the base material is 20° C. to 120° C.

<15> The manufacturing method of the conductive laminate described inany one of <6> to <14>, in which in the step of baking the firstconductive ink, a baking temperature is 250° C. or lower, and a bakingtime is 1 minute to 120 minutes.

<16> The manufacturing method of the conductive laminate described inany one of <6> to <15>, in which at the time of applying the secondconductive ink in the step of applying a second conductive ink, atemperature of the base material is 20° C. to 120° C.

<17> The manufacturing method of the conductive laminate described inany one of <6> to <16>, in which in the step of baking the secondconductive ink, a baking temperature is 250° C. or lower, and a bakingtime is 1 minute to 120 minutes.

<18> The manufacturing method of the conductive laminate described inany one of <6> to <17>, in which a time from when the step of applying afirst conductive ink has finished to when the step of baking the firstconductive ink is started is 60 seconds or less.

According to the present disclosure, there are provided a conductivelaminate having a low surface resistivity and excellent thermal cyclestability, and a manufacturing method of the conductive laminate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the conductive laminate and the manufacturing method of theconductive laminate of the present disclosure will be specificallydescribed.

In the present specification, a range of numerical values describedusing “to” means a range including numerical values described before andafter “to” as a minimum value and a maximum value, respectively.

Regarding the ranges of numerical values described stepwise in thepresent specification, the upper limit or the lower limit described in acertain range of numerical values may be replaced with the upper limitor the lower limit of another range of numerical values describedstepwise. In addition, in the ranges of numerical values described inthe present specification, the upper limit or the lower limit describedin a certain range of numerical values may be replaced with the valueshown in Examples.

In the present specification, in a case where there is a plurality ofsubstances in a composition that corresponds to each component of thecomposition, unless otherwise specified, the amount of each component ofthe composition means the total amount of the plurality of substancespresent in the composition.

In the present specification, a combination of two or more preferredembodiments is a more preferred embodiment.

In the present specification, the term “step” includes not only anindependent step but also a step which is not clearly distinguished fromanother step as long as the intended purpose of the step is achieved.

In the present specification, “image” means general films, and “imagerecording” means the formation of an image (that is, a film). In thepresent specification, the concept of “image” also includes a solidimage.

In the present specification, “thermal cycle stability” means that theconductive laminate has properties of experiencing a small change in asurface resistivity in a case where the conductive laminate isrepeatedly heated and cooled.

[Conductive Laminate]

The conductive laminate of the present disclosure comprises a basematerial and a conductive ink film provided on the base material, inwhich in a case where a surface of the conductive ink film close to thebase material is defined as a first main surface, and a surface of theconductive ink film far from the base material is defined as a secondmain surface, a first void ratio in a region that extends from the firstmain surface toward the second main surface to a position being awayfrom the first main surface by a distance equivalent to 50% of athickness of the conductive ink film is 15% to 50%, and a second voidratio in a region that extends from a position being away from thesecond main surface toward the first main surface by a distanceequivalent to 10% of the thickness of the conductive ink film to thesecond main surface is lower than the first void ratio.

The inventors of the present invention paid attention to the void ratiosin specific regions in the conductive ink film. As a result, theinventors have found that in a case where the first void ratio is 15% to50%, and the second void ratio is lower than the first void ratio, a lowsurface resistivity and high thermal cycle stability can besimultaneously achieved.

In the conductive laminate of the present disclosure, the first voidratio of the conductive ink film is 15% or more. Therefore, even thoughthe conductive laminate experiences volume change such as expansion orcontraction due to heat, defects such as peeling or breakage do notoccur, and excellent thermal cycle stability is exhibited. Furthermore,because the first void ratio of the conductive ink film in theconductive laminate of the present disclosure is 50% or less, thesurface resistivity is reduced.

In the conductive laminate of the present disclosure, the second voidratio of the conductive ink film is lower than the first void ratio.That is, because the region around the surface of the conductive inkfilm is dense, the surface resistivity is reduced.

Incidentally, JP2010-183082A does not pay attention to the void ratio ofthe conductive ink film. Furthermore, in a case where a conductivelaminate is prepared by the method disclosed in JP2010-183082A, the voidratio is substantially constant in the entire conductive ink film, and alow surface resistivity and high thermal cycle stability could not besimultaneously achieved.

<Base Material>

The conductive laminate of the present disclosure comprises a basematerial.

The material of the base material is not particularly limited, and canbe selected depending on the purpose. Specifically, examples of thematerial of the base material include synthetic resins such aspolyimide, polyethylene terephthalate, polybutylene terephthalate,polytrimethylene terephthalate, polyethylene naphthalate, polybutylenenaphthalate, polycarbonate, polyurethane, polyethylene, polypropylene,polyvinyl chloride, polystyrene, polyvinyl acetate, an acrylic resin, anacrylonitrile styrene resin (AS resin), anacrylonitrile-butadiene-styrene copolymer (ABS resin), triacetylcellulose, polyamide, polyacetal, polyphenylene sulfide, polysulfone, anepoxy resin, a glass epoxy resin, a melamine resin, a phenol resin, aurea resin, an alkyd resin, a fluororesin, and polylactic acid;inorganic materials such as copper, steel, aluminum, silicon, sodaglass, alkali-free glass, and indium tin oxide (ITO); and papers such asbase paper, art paper, coated paper, cast coated paper, resin coatedpaper, and synthetic paper. The base material may be composed of onelayer or two or more layers. In a case where the base material iscomposed of two or more layers, two or more base materials made ofdifferent materials may be laminated.

The base material is preferably in the form of a sheet or film. Thethickness of the base material is preferably 20 μm to 2,000 μm. In acase where the thickness of the base material is 20 μm or more, theconductive ink film can be stably maintained, and the handleability ofthe laminate on which the conductive ink film is formed is alsoimproved.

The base material may have an ink receiving layer. The thickness of theink receiving layer is preferably 1 μm to 20 μm. In a case where thethickness of the ink receiving layer is 1 μm to 20 μm, the ink receivinglayer can be more stably maintained, and the conductive ink morehomogeneously wets and spreads on the base material, which furtherimproves the quality of the conductive ink film. The ink receiving layeris a coating layer formed on the base material to absorb and fix ink.

In the conductive laminate of the present disclosure, from the viewpointof insulating properties and adhesiveness, the base material ispreferably a glass base material or a plastic base material.

<Conductive Ink Film>

In the conductive laminate of the present disclosure, the conductive inkfilm is provided on the base material. Although another layer may beprovided between the conductive ink film and the base material, it ispreferable that the conductive ink film be provided directly on the basematerial.

In the present disclosure, “conductivity” refers to properties of havinga surface resistivity of 1×10⁴ Ω/square or less.

In a case where a surface of the conductive ink film close to the basematerial is defined as a first main surface, and a surface of theconductive ink film far from the base material is defined as a secondmain surface, a first void ratio in a region that extends from the firstmain surface toward the second main surface to a position being awayfrom the first main surface by a distance equivalent to 50% of athickness of the conductive ink film is 15% to 50%, and a second voidratio in a region that extends from a position being away from thesecond main surface toward the first main surface by a distanceequivalent to 10% of the thickness of the conductive ink film to thesecond main surface is lower than the first void ratio.

In brief, in a case where the conductive ink film is divided intoregions in a thickness direction, the first void ratio in a 50% regionon a base material side in the thickness direction is 15% to 50%, andthe second void ratio in a 10% region on a non-base material side in thethickness direction is lower than the first void ratio. In a case wherethe first void ratio is 15% or more, even though the conductive laminateexperiences volume change such as expansion or contraction due to heat,defects such as peeling or breakage do not occur, and excellent thermalcycle stability is exhibited. In contrast, in a case where the firstvoid ratio is 50% or less, the surface resistivity is reduced.

Having the second void ratio lower than the first void ratio means thatthe 10% region on the non-base material side is denser than the 50%region on the base material side in the conductive ink film. In a casewhere the 10% region on the non-base material side is dense, the surfaceresistivity is reduced.

From the viewpoint of further improving the thermal cycle stability, thefirst void ratio is preferably 30% to 40%.

From the viewpoint of further reducing the surface resistivity, thesecond void ratio is preferably 20% or less, more preferably 10% orless, and even more preferably 7% or less. The lower limit of the secondvoid ratio is not particularly limited, and is, for example, 0%.

The difference between the first void ratio and the second void ratio isnot particularly limited. From the viewpoint of achieving both the lowsurface resistivity and thermal cycle stability, the difference ispreferably 5% to 40%, and more preferably 20% to 30%.

The void ratio in the conductive ink film can be controlled by the typeof conductive ink for forming the conductive ink film and bakingconditions after the application of the conductive ink. For example, ina case where an ink containing metal particles is used as the conductiveink, it is easy to form voids in the conductive ink film. In a casewhere an ink containing the metal particles is used, and the bakingtemperature is set to a high temperature, the void ratio is reduced. Inaddition, in a case where the baking time is increased, the void ratiois reduced.

The void ratio is measured, for example, by the following method.

By using a microtome (trade name RM2255, manufactured by LeicaBiosystems Nussloch GmbH), the conductive laminate is cut in a thicknessdirection of the conductive laminate, thereby obtaining a cross section.By using the cross section and a scanning electron microscope (tradename S-4700, manufactured by Hitachi High-Tech Corporation.), across-sectional observation image is obtained.

By using image software (“Adobe Photoshop” manufactured by AdobeSystems, Inc.), threshold values of the obtained cross-sectionalobservation image are adjusted to obtain a binary image including awhite region where a conductive substance is present and a black regionwhere voids are present. In the obtained image, the projection portionsat five upper points and the recess portions at five lower points on theside of the ink film surface are averaged, and the position obtained inthis way is adopted as an upper side. Furthermore, for the base materialside of the ink film, the same calculation as above is performed, andthe position obtained by the calculation is adopted as a lower side. Thespace between the upper side and the lower side is divided into 10 equalparts, and a region from the lower side to the 5th part is defined as a50% region on the base material side, and a region from the 9th partfrom the base material side to the upper region is defined as a 10%region on the non-base material side.

The first void ratio is calculated as a ratio of the area of the blackregion (void) to the total area of the 50% region on the base materialside in the cross-sectional observation image.

The second void ratio is calculated as a ratio of the area of the blackregion (void) to the total area of the 10% region on the non-basematerial side in the cross-sectional observation image.

The conductive ink film preferably contains a conductive substance, andthe conductive substance is preferably a metal. Examples of the metalinclude a base metal and a noble metal. Examples of the base metalinclude nickel, titanium, cobalt, copper, chromium, manganese, iron,zirconium, tin, tungsten, molybdenum, and vanadium. Examples of thenoble metal include gold, silver, platinum, palladium, iridium, osmium,ruthenium, rhodium, rhenium, and alloys containing these metals. Fromthe viewpoint of conductivity, the conductive ink film preferablycontains at least one metal selected from the group consisting ofsilver, gold, platinum, nickel, palladium, and copper, and morepreferably contains silver.

In the conductive ink film, the content of a metal with respect to thetotal amount of the conductive ink film is preferably 5% by mass to 70%by mass, and more preferably 7% by mass to 50% by mass.

The thickness of the conductive ink film is not particularly limited.From the viewpoint of productivity and conductivity, the thickness ofthe conductive ink film is preferably 0.5 μm to 30 μm, and morepreferably 5 μm to 20 μm.

[Manufacturing Method of Conductive Laminate]

The manufacturing method of the conductive laminate of the presentdisclosure is not particularly limited as long as the conductive inkfilm can be formed on a base material.

The conductive ink film can be formed, for example, by applying theconductive ink onto a base material, and then baking the conductive inkapplied onto the base material. The conductive ink film may be formed byrepeating the application of the conductive ink and the baking of theconductive ink film multiple times.

The conductive ink is preferably an ink containing metal particles(hereinafter, also called “metal particle ink”), an ink containing ametal complex (hereinafter, also called “metal complex ink”), or an inkcontaining a metal salt (hereinafter, also called “metal salt ink”), andmore preferably a metal particle ink or a metal complex ink.

<Metal Particle Ink>

The metal particle ink is, for example, an ink composition obtained bydispersing metal particles in a dispersion medium.

(Metal Particles)

Examples of the metal constituting the metal particles include particlesof a base metal and a noble metal. Examples of the base metal includenickel, titanium, cobalt, copper, chromium, manganese, iron, zirconium,tin, tungsten, molybdenum, and vanadium. Examples of the noble metalinclude gold, silver, platinum, palladium, iridium, osmium, ruthenium,rhodium, rhenium, and alloys containing these metals. Among these, fromthe viewpoint of conductivity, the metal constituting the metalparticles preferably includes at least one metal selected from the groupconsisting of silver, gold, platinum, nickel, palladium, and copper, andmore preferably includes silver.

The average particle diameter of the metal particles is not particularlylimited, but is preferably 10 nm to 500 nm, and more preferably 10 nm to200 nm. In a case where the average particle diameter is in the aboverange, the baking temperature of the metal particles is lowered, whichimproves the process suitability for preparing the conductive ink film.Particularly, in a case where the metal particle ink is applied using aspray method or an ink jet recording method, jettability is improved,which tends to improve pattern forming properties and film thicknessuniformity of the conductive ink film. The average particle diametermentioned herein means the average of primary particle diameters of themetal particles (average primary particle diameter).

For example, by using a laser diffraction/scattering-type particle sizedistribution analyzer (trade name “LA-960”, manufactured by Horiba,Ltd.), a 50% cumulative volume-based diameter (D50) of the metalparticles is measured three times, and the average of the diametersmeasured three times is calculated and adopted as the average particlediameter of the metal particles.

As necessary, the metal particle ink may contain metal particles havingan average particle diameter of 500 nm or more. In a case where themetal particle ink contains metal particles having an average particlediameter of 500 nm or more, the nm-sized metal particles lower themelting point around the μm-sized metal particles, which makes itpossible to bond the conductive ink film.

In the metal particle ink, the content of the metal particles withrespect to the total amount of the metal particle ink is preferably 10%by mass to 90% by mass, and more preferably 20% by mass to 50% by mass.In a case where the content of the metal particles is 10% by mass ormore, the surface resistivity is further reduced. In a case where thecontent of the metal particles is 90% by mass or less, jettability isimproved in a case where the metal particle ink is applied using a spraymethod or an ink jet recording method.

In addition to the metal particles, the metal particle ink may contain,for example, a dispersant, a resin, a dispersion medium, a thickener,and a surface tension adjuster.

(Dispersant)

The metal particle ink may contain a dispersant that adheres to at leasta part of the surface of the metal particles. The dispersantsubstantially constitutes metal colloidal particles, together with themetal particles. The dispersant has an action of coating the metalparticles to improve the dispersibility of the metal particles andprevent aggregation. The dispersant is preferably an organic compoundcapable of forming metal colloidal particles. From the viewpoint ofconductivity and dispersion stability, the dispersant is preferably anamine compound, a carboxylic acid, an alcohol, or a resin dispersant.

The metal particle ink may contain one dispersant or two or moredispersants.

Examples of the amine compound include saturated or unsaturatedaliphatic amines. Among these, an aliphatic amine having 4 to 8 carbonatoms is preferable as the amine compound. The aliphatic amine having 4to 8 carbon atoms may be linear or branched, or may have a ringstructure.

Examples of the aliphatic amine include butylamine, normal pentylamine,isopentylamine, hexylamine, 2-ethylhexylamine, and octylamine.

Examples of the amine having an alicyclic structure includecycloalkylamines such as cyclopentylamine and cyclohexylamine.

Examples of an aromatic amine include aniline.

The amine compound may have a functional group other than an aminogroup. Examples of the functional group other than an amino groupinclude a hydroxy group, a carboxy group, an alkoxy group, a carbonylgroup, an ester group, and a mercapto group.

Examples of the carboxylic acid include formic acid, oxalic acid, aceticacid, hexanoic acid, acrylic acid, octylic acid, and oleic acid. Thecarboxy group which is a part of the carboxylic acid may form a saltwith a metal ion. The salt may be formed of one metal ion or two or moremetal ions.

The carboxylic acid may have a functional group other than the carboxygroup. Examples of the functional group other than the carboxy groupinclude an amino group, a hydroxy group, an alkoxy group, a carbonylgroup, an ester group, and a mercapto group.

Examples of the alcohol include a terpene-based alcohol, an allylalcohol, an oleyl alcohol, tianshic acid, ricinoleic acid, gallic acid,and salicylic acid. The alcohol is likely to be coordinated with thesurface of the metal particles and can suppress aggregation of the metalparticles.

Examples of the resin dispersant include a dispersant that has anonionic group as a hydrophilic group and can be homogeneously dissolvedin a solvent. Examples of the resin dispersant includepolyvinylpyrrolidone, polyethylene glycol, a polyethyleneglycol-polypropylene glycol copolymer, polyvinyl alcohol,polyallylamine, and a polyvinyl alcohol-polyvinyl acetate copolymer. Themolecular weight of the resin dispersant is preferably 1,000 to 50,000,and more preferably 1,000 to 30,000, in terms of a weight-averagemolecular weight.

In the metal particle ink, the content of the dispersant with respect tothe total amount of the metal particle ink is preferably 0.5% by mass to50% by mass, and more preferably 1% by mass to 30% by mass.

(Dispersion Medium)

It is preferable that the metal particle ink contain a dispersionmedium. The type of dispersion medium is not particularly limited, andexamples thereof include a hydrocarbon, an alcohol, and water.

The metal particle ink may contain one dispersion medium or two or moredispersion media. It is preferable that the dispersion medium containedin the metal particle ink be volatile. The boiling point of thedispersion medium is preferably 50° C. to 250° C., more preferably 70°C. to 220° C., and even more preferably 80° C. to 200° C. In a casewhere the boiling point of the dispersion medium is 50° C. to 250° C.,the stability and baking properties of the metal particle ink tend to besimultaneously achieved.

Examples of the hydrocarbon include an aliphatic hydrocarbon and anaromatic hydrocarbon.

Examples of the aliphatic hydrocarbon include a saturated or unsaturatedaliphatic hydrocarbon such as tetradecane, octadecane,heptamethylnonane, tetramethylpentadecane, hexane, heptane, octane,nonane, decane, tridecane, methylpentane, normal paraffin, orisoparaffin.

Examples of the aromatic hydrocarbon include toluene and xylene.

Examples of the alcohol include an aliphatic alcohol and an alicyclicalcohol. In a case where an alcohol is used as the dispersion medium,the dispersant is preferably an amine compound or a carboxylic acid.

Examples of the aliphatic alcohol include a saturated or unsaturatedaliphatic alcohol having 6 to 20 carbon atoms that may contain an etherbond in a chain, such as heptanol, octanol (for example, 1-octanol,2-octanol, 3-octanol, or the like), decanol (for example, 1-decanol orthe like), lauryl alcohol, tetradecyl alcohol, cetyl alcohol,2-ethyl-1-hexanol, octadecyl alcohol, hexadecenol, and oleyl alcohol.

Examples of the alicyclic alcohol include a cycloalkanol such ascyclohexanol; a terpene alcohol such as terpineol (including a, (3, andy isomers, or any mixture of these) or dihydroterpineol; myrtenol,sobrerol, menthol, carveol, perillyl alcohol, pinocarveol, and verbenol.

The dispersion medium may be water. From the viewpoint of adjustingphysical properties such as viscosity, surface tension, and volatility,the dispersion medium may be a mixed solvent of water and anothersolvent. Another solvent to be mixed with water is preferably analcohol. The alcohol used together with water is preferably an alcoholthat is miscible with water and has a boiling point of 130° C. or lower.Examples of the alcohol include 1-propanol, 2-propanol, 1-butanol,2-butanol, tert-butanol, 1-pentanol, ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, ethylene glycol monopropyl ether,propylene glycol monomethyl ether.

In the metal particle ink, the content of the dispersion medium ispreferably 1% by mass to 50% by mass with respect to the total amount ofthe metal particle ink. In a case where the content of the dispersionmedium is 1% by mass to 50% by mass, the metal particle ink can obtainsufficient conductivity as a conductive ink. The content of thedispersion medium is more preferably 10% by mass to 45% by mass, andeven more preferably 20% by mass to 40% by mass.

(Resin)

The metal particle ink may contain a resin. Examples of the resininclude polyester, polyurethane, a melamine resin, an acrylic resin, astyrene-based resin, a polyether resin, and a terpene resin.

The metal particle ink may contain one resin or two or more resins.

In the metal particle ink, the content of the resin is preferably 0.1%by mass to 5% by mass with respect to the total amount of the metalparticle ink.

(Thickener)

The metal particle ink may contain a thickener. Examples of thethickener include clay minerals such as clay, bentonite, and hectorite;cellulose derivatives such as methyl cellulose, carboxymethyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropylmethyl cellulose; and polysaccharides such as xanthan gum and guar gum.

The metal particle ink may contain one thickener or two or morethickeners.

In the metal particle ink, the content of the thickener is preferably0.1% by mass to 5% by mass with respect to the total amount of the metalparticle ink.

(Surfactant)

The metal particle ink may contain a surfactant. In a case where themetal particle ink contains a surfactant, a uniform conductive ink filmis likely to be formed.

The surfactant may be any of an anionic surfactant, a cationicsurfactant, and a nonionic surfactant. Among these, as the surfactant, afluorine-based surfactant is preferable, because this surfactant makesit possible to adjust the surface tension even though the metal particleink contains a small amount of such a surfactant. Furthermore, thesurfactant is preferably a compound having a boiling point higher than250° C.

The viscosity of the metal particle ink is not particularly limited. Theviscosity of the metal particle ink may be 0.01 Pa·s to 5,000 Pa·s, andis preferably 0.1 Pa·s to 100 Pas. In a case where the metal particleink is applied using a spray method or an ink jet recording method, theviscosity of the metal particle ink is preferably 1 mPa·s to 100 mPa·s,more preferably 2 mPa·s to 50 mPa·s, and even more preferably 3 mPa·s to30 mPa·s.

The viscosity of the metal particle ink is a value measured at 25° C. byusing a viscometer. The viscosity is measured, for example, using aVISCOMETER TV-22 type viscometer (manufactured by TOKISANGYO).

The surface tension of the metal particle ink is not particularlylimited, and is preferably 20 mN/m to 45 mN/m and more preferably 25mN/m to 40 mN/m. The surface tension is a value measured at 25° C. byusing a surface tensiometer. The surface tension is measured using, forexample, DY-700 (manufactured by Kyowa Interface Science Co., Ltd.).

(Manufacturing Method of Metal Particles)

The metal particles may be a commercially available product or may bemanufactured by a known method. Examples of the manufacturing method ofthe metal particles include a wet reduction method, a vapor phasemethod, and a plasma method. Preferred examples of the manufacturingmethod of the metal particles include a wet reduction method capable ofmanufacturing metal particles having an average particle diameter of 200nm or less and having a narrow particle size distribution. Examples ofthe manufacturing method of the metal particles by a wet reductionmethod include the method described in JP2017-37761A, WO2014-57633A1,and the like, the method including a step of mixing a metal salt with areducing agent to obtain a complexing reaction solution and a step ofheating the complexing reaction solution to reduce metal ions in thecomplexing reaction solution and to obtain a slurry of metalnanoparticles.

In manufacturing the metal particle ink, a heating treatment may beperformed such that the content of each component contained in the metalparticle ink is adjusted to be in a predetermined range. The heatingtreatment may be performed under reduced pressure or under normalpressure. In a case where the heating treatment is performed undernormal pressure, the heating treatment may be performed in theatmosphere or in an inert gas atmosphere.

<Metal Complex Ink>

The metal complex ink is, for example, an ink composition obtained bydissolving a metal complex in a solvent.

Examples of metals constituting the metal complex include silver,copper, gold, aluminum, magnesium, tungsten, molybdenum, zinc, nickel,iron, platinum, tin, copper, and lead. Among these, from the viewpointof conductivity, the metal constituting the metal complex preferablyincludes at least one metal selected from the group consisting ofsilver, gold, platinum, nickel, palladium, and copper, and morepreferably includes silver.

The content of the metal contained in the metal complex ink with respectto the total amount of the metal complex ink is preferably 1% by mass to40% by mass, more preferably 5% by mass to 30% by mass, and even morepreferably 7% by mass to 20% by mass, in terms of the metal element.

The metal complex can be obtained, for example, by reacting a metal saltwith a complexing agent. Examples of the manufacturing method of themetal complex include a method of adding a metal salt and a complexingagent to an organic solvent and stirring the mixture for a predeterminedtime. The stirring method is not particularly limited, and can beappropriately selected from known methods such as a stirring methodusing a stirrer, a stirring blade, or a mixer, and a method of applyingultrasonic waves.

Examples of the metal salt include a metal oxide, thiocyanate, sulfide,chloride, cyanide, cyanate, carbonate, acetate, nitrate, nitrite,sulfate, phosphate, perchlorate, tetrafluoroborate, an acetyl acetonatecomplex salt, and carboxylate.

Examples of the complexing agent include an amine compound, an ammoniumcarbamate-based compound, an ammonium carbonate-based compound, anammonium bicarbonate compound, and a carboxylic acid. Among these, fromthe viewpoint of the conductivity and the stability of the metalcomplex, it is preferable that the complexing agent include at least onecompound selected from the group consisting of an ammoniumcarbamate-based compound, an ammonium carbonate-based compound, analkylamine, and a carboxylic acid having 8 to 20 carbon atoms.

The metal complex has a structure derived from a complexing agent. It ispreferable that the metal complex have a structure derived from at leastone compound selected from the group consisting of an ammoniumcarbamate-based compound, an ammonium carbonate-based compound, analkylamine, and a carboxylic acid having 8 to 20 carbon atoms.

Examples of the amine compound as a complexing agent include ammonia, aprimary amine, a secondary amine, a tertiary amine, and a polyamine.

Examples of the primary amine having a linear alkyl group includemethylamine, ethylamine, 1-propylamine, n-butylamine, n-pentylamine,n-hexylamine, heptylamine, octylamine, nonylamine, n-decylamine,undecylamine, dodecylamine, tridecylamine, tetradecylamine,pentadecylamine, hexadecylamine, heptadecylamine, and octadecylamine.

Examples of the primary amine having a branched alkyl group includeisopropylamine, sec-butylamine, tert-butylamine, isopentylamine,2-ethylhexylamine, and tert-octylamine.

Examples of the primary amine having an alicyclic structure includecyclohexylamine and dicyclohexylamine.

Examples of the primary amine having a hydroxyalkyl group includeethanolamine, diethanolamine, triethanolamine, N-methylethanolamine,propanolamine, isopropanolamine, dipropanolamine, diisopropanolamine,tripropanolamine, and triisopropanolamine.

Examples of the primary amine having an aromatic ring includebenzylamine, N,N-dimethylbenzylamine, phenylamine, diphenylamine,triphenylamine, aniline, N,N-dim ethyl aniline,N,N-dimethyl-p-toluidine, 4-aminopyridine, and 4-dimethylaminopyridine.

Examples of the secondary amine include dimethylamine, diethylamine,dipropylamine, dibutylamine, diphenylamine, dicyclopentylamine, andmethylbutylamine.

Examples of the tertiary amine include trimethylamine, triethylamine,tripropylamine, and triphenylamine.

Examples of the polyamine include ethylenediamine, 1,3-diaminopropane,diethylenetriamine, triethylenetetramine, tetramethylenepentamine,hexamethylenediamine, tetraethylenepentamine, and a combination ofthese.

The amine compound is preferably an alkylamine, more preferably analkylamine having 3 to 10 carbon atoms, and even more preferably aprimary alkylamine having 4 to 10 carbon atoms.

The metal complex may be configured with one amine compound or two ormore amine compounds.

In reacting the metal salt with an amine compound, the ratio of themolar amount of the amine compound to the molar amount of the metal saltis preferably 1/1 to 15/1, and more preferably 1.5/1 to 6/1. In a casewhere the above ratio is within the above range, the complex formationreaction goes to completion, and a transparent solution is obtained.

Examples of the ammonium carbamate-based compound as a complexing agentinclude ammonium carbamate, methyl ammonium methylcarbamate,ethylammonium ethylcarbamate, 1-propylammonium 1-propylcarbamate,isopropylammonium isopropylcarbamate, butylammonium butylcarbamate,isobutylammonium isobutylcarbamate, amylammonium amylcarbamate,hexylammonium hexylcarbamate, heptylammonium heptylcarbamate,octylammonium octylcarbamate, 2-ethylhexylammonium2-ethylhexylcarbamate, nonylammonium nonylcarbamate, and decylammoniumdecylcarbamate.

Examples of the ammonium carbonate-based compound as a complexing agentinclude ammonium carbonate, methylammonium carbonate, ethylammoniumcarbonate, 1-propylammonium carbonate, isopropylammonium carbonate,butylammonium carbonate, isobutylammonium carbonate, amylammoniumcarbonate, hexylammonium carbonate, heptylammonium carbonate,octylammonium carbonate, 2-ethylhexylammonium carbonate, nonylammoniumcarbonate, and decylammonium carbonate.

Examples of the ammonium bicarbonate-based compound as a complexingagent include ammonium bicarbonate, methylammonium bicarbonate,ethylammonium bicarbonate, 1-propylammonium bicarbonate,isopropylammonium bicarbonate, butylammonium bicarbonate,isobutylammonium bicarbonate, amylammonium bicarbonate, hexylammoniumbicarbonate, heptylammonium bicarbonate, octylammonium bicarbonate,2-ethylhexylammonium bicarbonate, nonylammonium bicarbonate, anddecylammonium bicarbonate.

In reacting the metal salt with an ammonium carbamate-based compound, anammonium carbonate-based compound, or an ammonium bicarbonate-basedcompound, the ratio of the molar amount of the ammonium carbamate-basedcompound, the ammonium carbonate-based compound, or the ammoniumbicarbonate-based compound to the molar amount of the metal salt ispreferably 0.01/1 to 1/1, and more preferably 0.05/1 to 0.6/1.

Examples of the carboxylic acid as a complexing agent include caproicacid, caprylic acid, pelargonic acid, 2-ethylhexanoic acid, capric acid,neodecanoic acid, undecanoic acid, lauric acid, myristic acid, palmiticacid, stearic acid, palmitoleic acid, oleic acid, linoleic acid, andlinolenic acid. Among these, as the carboxylic acid, a carboxylic acidhaving 8 to 20 carbon atoms is preferable, and a carboxylic acid having10 to 16 carbon atoms is more preferable.

In the metal complex ink, the content of the metal complex with respectto the total amount of the metal complex ink is preferably 10% by massto 90% by mass, and more preferably 10% by mass to 40% by mass. In acase where the content of the metal complex is 10% by mass or more, thesurface resistivity is further reduced. In a case where the content ofthe metal complex is 90% by mass or less, jettability is improved in acase where the metal complex ink is applied using a spray method or anink jet recording method.

(Solvent)

It is preferable that the metal complex ink contain a solvent. Thesolvent is not particularly limited as long as it can dissolve thecomponent contained in the metal complex ink, such as the metal complex.From the viewpoint of ease of manufacturing, the boiling point of thesolvent is preferably 30° C. to 300° C., more preferably 50° C. to 200°C., and even more preferably 50° C. to 150° C.

The content of the solvent in the conductive ink is preferably set suchthat the concentration of metal ions with respect to the metal complex(the amount of the metal present as free ions with respect to 1 g of themetal complex) is 0.01 mmol/g to 3.6 mmol/g, and more preferably setsuch that the aforementioned concentration of metal ions is 0.05 mmol/gto 2 mmol/g. In a case where the concentration of metal ions is withinthe above range, the metal complex ink has excellent fluidity and canobtain conductivity.

Examples of the solvent include a hydrocarbon, a cyclic hydrocarbon, anaromatic hydrocarbon, a carbamate, an alkene, an amide, an ether, anester, an alcohol, a thiol, a thioether, phosphine, and water. The metalcomplex ink may contain only one solvent or two or more solvents.

The hydrocarbon is preferably a linear or branched hydrocarbon having 6to 20 carbon atoms. Examples of the hydrocarbon include pentane, hexane,heptane, octane, nonane, decane, undecane, dodecane, tridecane,tetradecane, pentadecane, hexadecane, octadecane, nonadecane, andicosane.

The cyclic hydrocarbon is preferably a cyclic hydrocarbon having 6 to 20carbon atoms.

The cyclic hydrocarbons can include, for example, cyclohexane,cycloheptane, cyclooctane, cyclononane, cyclodecane, and decalin.

Examples of the aromatic hydrocarbon include benzene, toluene, xylene,and tetraline.

The ether may be any of a linear ether, a branched ether, and a cyclicether. Examples of the ether include diethyl ether, dipropyl ether,dibutyl ether, methyl-t-butyl ether, tetrahydrofuran, tetrahydropyrane,dihydropyrane, and 1,4-dioxane.

The alcohol may be any of a primary alcohol, a secondary alcohol, and atertiary alcohol.

Examples of the alcohol include ethanol, 1-propanol, 2-propanol,1-methoxy-2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol,3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-octanol, 2-octanol,3-octanol, tetrahydrofurfuryl alcohol, cyclopentanol, terpineol,decanol, isodecyl alcohol, lauryl alcohol, isolauryl alcohol, myristylalcohol, isomyristyl alcohol, cetyl alcohol (cetanol), isocetyl alcohol,stearyl alcohol, isostearyl alcohol, oleyl alcohol, isooleyl alcohol,linoleyl alcohol, isolinoleyl alcohol, palmityl alcohol, isopalmitylalcohol, icosyl alcohol, and isoicosyl alcohol.

Examples of the ketone include acetone, methyl ethyl ketone, methylisobutyl ketone, and cyclohexanone.

Examples of the ester include methyl acetate, ethyl acetate, isopropylacetate, butyl acetate, isobutyl acetate, sec-butyl acetate,methoxybutyl acetate, ethylene glycol monomethyl ether acetate, ethyleneglycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate,diethylene glycol monomethyl ether acetate, diethylene glycol monoethylether acetate, diethylene glycol monobutyl ether acetate, propyleneglycol monomethyl ether acetate, propylene glycol monoethyl etheracetate, propylene glycol monobutyl ether acetate, dipropylene glycolmonomethyl ether acetate, dipropylene glycol monoethyl ether acetate,dipropylene glycol monobutyl ether acetate, and 3-methoxybutyl acetate.

(Reducing Agent)

The metal complex ink may contain a reducing agent. In a case where themetal complex ink contains a reducing agent, the reduction of the metalcomplex into a metal is facilitated.

Examples of the reducing agent include a borohydride metal salt, analuminum hydride salt, an amine compound, an alcohol, an organic acid,reduced sugar, a sugar alcohol, sodium sulfite, a hydrazine compound,dextrin, hydroquinone, hydroxylamine, ethylene glycol, glutathione, andan oxime compound.

The reducing agent may be the oxime compound described inJP2014-516463A.

Examples of the oxime compound include acetone oxime, cyclohexanoneoxime, 2-butanone oxime, 2,3-butanedione monoxime, dimethyl glyoxime,methyl acetoacetate monoxime, methyl pyruvate monoxime, benzaldehydeoxime, 1-indanone oxime, 2-adamantanone oxime, 2-methylbenzamide oxime,3-methylbenzamide oxime, 4-methylbenzamide oxime, 3-aminobenzamideoxime, 4-aminobenzamide oxime, acetophenone oxime, benzamide oxime, andpinacolone oxime.

The metal complex ink may contain one reducing agent or two or morereducing agents.

The content of the reducing agent in the metal complex ink is notparticularly limited, but is preferably 0.1% by mass to 20% by mass,more preferably 0.3% by mass to 10% by mass, and even more preferably 1%by mass to 5% by mass.

(Resin)

The metal complex ink may contain a resin. In a case where the metalcomplex ink contains a resin, the adhesiveness of the metal complex inkto the base material is improved.

Examples of the resin include polyester, polyethylene, polypropylene,polyacetal, polyolefin, polycarbonate, polyamide, a fluororesin, asilicone resin, ethyl cellulose, hydroxyethyl cellulose, rosin, anacrylic resin, polyvinyl chloride, polysulfone, polyvinylpyrrolidone,polyvinyl alcohol, a polyvinyl-based resin, polyacrylonitrile,polysulfide, polyamideimide, polyether, polyarylate, polyether etherketone, polyurethane, an epoxy resin, a vinyl ester resin, a phenolresin, a melamine resin, and a urea resin.

The metal complex ink may contain one resin or two or more resins.

(Additive)

As long as the effects of the present disclosure are not reduced, themetal complex ink may further contain additives such as an inorganicsalt, an organic salt, an inorganic oxide such as silica, a surfaceconditioner, a wetting agent, a crosslinking agent, an antioxidant, arust inhibitor, a heat-resistant stabilizer, a surfactant, aplasticizer, a curing agent, a thickener, and a silane coupling agent.In the metal complex ink, the total content of additives is preferably20% by mass or less with respect to the total amount of the metalcomplex ink.

The viscosity of the metal complex ink is not particularly limited. Theviscosity of the metal complex ink may be 0.01 Pa·s to 5,000 Pa·s, andis preferably 0.1 Pa·s to 100 Pa·s. In a case where the metal complexink is applied using a spray method or an ink jet recording method, theviscosity of the metal complex ink is preferably 1 mPa·s to 100 mPa·s,more preferably 2 mPa·s to 50 mPa·s, and even more preferably 3 mPa·s to30 mPa·s.

The viscosity of the metal complex ink is a value measured at 25° C. byusing a viscometer. The viscosity is measured, for example, using aVISCOMETER TV-22 type viscometer (manufactured by TOKISANGYO).

The surface tension of the metal complex ink is not particularlylimited, and is preferably 20 mN/m to 45 mN/m and more preferably 25mN/m to 35 mN/m. The surface tension is a value measured at 25° C. byusing a surface tensiometer. The surface tension is measured using, forexample, DY-700 (manufactured by Kyowa Interface Science Co., Ltd.).

<Metal Salt Ink>

The metal salt ink is, for example, an ink composition obtained bydissolving a metal salt in a solvent.

Examples of metals constituting the metal salt include silver, copper,gold, aluminum, magnesium, tungsten, molybdenum, zinc, nickel, iron,platinum, tin, copper, and lead. Among these, from the viewpoint ofconductivity, the metal constituting the metal salt preferably includesat least one metal selected from the group consisting of silver, gold,platinum, nickel, palladium, and copper, and more preferably includessilver.

The content of the metal contained in the metal salt ink with respect tothe total amount of the metal salt ink is preferably 1% by mass to 40%by mass, more preferably 5% by mass to 30% by mass, and even morepreferably 7% by mass to 20% by mass, in terms of the metal element.

In the metal salt ink, the content of the metal salt with respect to thetotal amount of the metal salt ink is preferably 10% by mass to 90% bymass, and more preferably 10% by mass to 40% by mass. In a case wherethe content of the metal salt is 10% by mass or more, the surfaceresistivity is further reduced. In a case where the content of the metalsalt is 90% by mass or less, jettability is improved in a case where themetal salt ink is applied using a spray method or an ink jet recordingmethod.

Examples of the metal salt include benzoate, halide, carbonate, citrate,iodate, nitrite, nitrate, acetate, phosphate, sulfate, sulfide,trifluoroacetate, and carboxylate of a metal. It should be noted thattwo or more salts may be combined.

From the viewpoint of conductivity and storage stability, the metal saltis preferably a metal carboxylate. The carboxylic acid forming thecarboxylate is preferably at least one compound selected from the groupconsisting of formic acid and a carboxylic acid having 1 to 30 carbonatoms, and more preferably a carboxylic acid having 8 to 20 carbonatoms, and even more preferably a fatty acid having 8 to 20 carbonatoms. The fatty acid may be linear or branched or may have asubstituent.

Examples of the linear fatty acid include acetic acid, propionic acid,butyric acid, valeric acid, pentanoic acid, hexanoic acid, heptanoicacid, behenic acid, oleic acid, octanoic acid, nonanoic acid, decanoicacid, caproic acid, enanthic acid, caprylic acid, pelargonic acid,capric acid, and undecanoic acid.

Examples of the branched fatty acid include isobutyric acid, isovalericacid, ethylhexanoic acid, neodecanoic acid, pivalic acid,2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid,2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid,3,3-dimethylbutanoic acid, and 2-ethylbutanoic acid.

Examples of the carboxylic acid having a substituent includehexafluoroacetylacetonate, hydroangelate, 3-hydroxybutyric acid,2-methyl-3-hydroxybutyric acid, 3-methoxybutyric acid,acetonedicarboxylic acid, 3-hydroxyglutaric acid,2-methyl-3-hydroxyglutaric acid, and 2,2,4,4-hydroxyglutaric acid.

The metal salt may be a commercially available product or may bemanufactured by a known method. For example, a silver salt ismanufactured by the following method.

First, a silver compound (for example, silver acetate) functioning as asilver supply source and formic acid or a fatty acid having 1 to 30carbon atoms in the same quantity as the molar equivalent of the silvercompound are added to an organic solvent such as ethanol. The mixture isstirred for a predetermined time by using an ultrasonic stirrer, and theformed precipitate is washed with ethanol and decanted. All of thesesteps can be performed at room temperature. The mixing ratio of thesilver compound and the formic acid or fatty acid having 1 to 30 carbonatoms is preferably 1:2 to 2:1, and more preferably 1:1, in terms ofmolar ratio.

The metal salt ink may contain a solvent, a reducing agent, a resin, andadditives. Preferred aspects of the solvent, reducing agent, resin, andadditives are the same as the preferred aspects of the solvent, reducingagent, resin, and additives which may be contained in the metal complexink.

The viscosity of the metal salt ink is not particularly limited. Theviscosity of the metal salt ink may be 0.01 Pas to 5,000 Pa·s, and ispreferably 0.1 Pa·s to 100 Pa·s. In a case where the metal salt ink isapplied using a spray method or an ink jet recording method, theviscosity of the metal salt ink is preferably 1 mPa·s to 100 mPa·s, morepreferably 2 mPa·s to 50 mPa·s, and even more preferably 3 mPa·s to 30mPa·s.

The viscosity of the metal salt ink is a value measured at 25° C. byusing a viscometer. The viscosity is measured, for example, using aVISCOMETER TV-22 type viscometer (manufactured by TOKISANGYO).

The surface tension of the metal salt ink is not particularly limited,and is preferably 20 mN/m to 45 mN/m and more preferably 25 mN/m to 35mN/m. The surface tension is a value measured at 25° C. by using asurface tensiometer. The surface tension is measured using, for example,DY-700 (manufactured by Kyowa Interface Science Co., Ltd.).

The manufacturing method of the conductive laminate of the presentdisclosure includes a step of applying at least one conductive inkselected from the group consisting of the metal particle ink, metalcomplex ink, and metal salt ink described above onto a base material,and a step of baking the applied conductive ink, and it is preferablethat the step of applying the conductive ink and the step of baking theconductive ink be repeated two or more times. In addition, in themanufacturing method of the conductive laminate of the presentdisclosure, the conductive ink may be applied multiple times and thenbaked. Particularly, in order to obtain a conductive laminate having afirst void ratio of 15% to 50% and a second void ratio that is lowerthan the first void ratio, it is preferable that the manufacturingmethod of the conductive laminate of the present disclosure include astep of applying the metal particle ink onto a base material and a stepof baking the metal particle ink.

Examples of preferred aspects of the manufacturing method of theconductive laminate of the present disclosure include the followingaspects.

(1) A method of performing a step of applying a metal particle ink, abaking step, a step of applying a metal complex ink, and a baking stepin this order.

(2) A method of performing a step of applying a metal particle ink, abaking step, a step of applying a metal particle ink, and a baking stepin this order.

(3) A method of performing a step of applying a metal complex ink, abaking step, a step of applying a metal complex ink, and a baking stepin this order.

(4) A method of performing a step of applying a metal particle ink, abaking step, a step of applying a metal complex ink, a baking step, astep of applying a metal complex ink, and a baking step in this order.

(5) A method of performing a step of applying a metal particle ink, abaking step, a step of applying a metal complex ink, a baking step, astep of applying a metal complex ink, a baking step, a step of applyinga metal complex ink, and a baking step in this order.

(6) A method of performing a step of applying a metal particle ink, abaking step, a step of applying a metal particle ink, a baking step, astep of applying a metal particle ink, a baking step, a step of applyinga metal complex ink, and a baking step in this order.

In a preferred aspect of the above manufacturing method, in a case wherethe manufacturing method includes a step of applying a metal particleink that is performed two or more times, the metal particle inks used inthe steps may be the same as or different from each other. In addition,in a case where the manufacturing method includes a step of applying ametal complex ink that is performed two or more times, the metal complexinks used in the steps may be the same as or different from each other.The same two inks mean that the inks contain the same type of componentsat the same content. The two different inks mean that at least the typeor content of components contained in the inks varies between the inks.

In a preferred aspect of the above manufacturing method, the bakingtemperature and baking time may be the same for the baking steps or mayvary between the baking steps.

Particularly, it is preferable that the manufacturing method of theconductive laminate of the present disclosure include a step of applyinga first conductive ink containing metal particles onto a base material(hereinafter, called “first applying step”), a step of baking the firstconductive ink (hereinafter, called “first baking step”), a step ofapplying a second conductive ink containing a metal salt or a metalcomplex onto the baked first conductive ink (hereinafter, called “secondapplying step”), and a step of baking the second conductive ink(hereinafter, called “second baking step”).

(First Applying Step)

The first applying step is a step of applying a first conductive inkcontaining metal particles onto a base material. Details of the basematerial are as described above.

The method of applying the first conductive ink onto the base materialis not particularly limited, and examples thereof include known methodssuch as a coating method, an ink jet recording method, and a dippingmethod. Among these, from the viewpoint of making it possible to form athin conductive ink film by applying once a small amount of the firstconductive ink by means of jetting, it is preferable that the firstconductive ink be applied using an ink jet recording method in the firstapplying step.

The ink jet recording method may be any of an electric charge controlmethod of jetting an ink by using electrostatic attraction force, adrop-on-demand method using the vibration pressure of a piezo element(pressure pulse method), an acoustic ink jet method of jetting an ink byusing radiation pressure by means of converting electric signals intoacoustic beams and irradiating the ink with the acoustic beams, and athermal ink jet (Bubble Jet (registered trademark)) method of formingbubbles by heating an ink and using the generated pressure.

As the ink jet recording method, particularly, it is possible toeffectively use the method described in JP1979-59936A (JP-S54-59936A),which is an ink jet recording method of causing an ink to experience arapid volume change by the action of thermal energy and jetting the inkfrom a nozzle by using the acting force resulting from the change ofstate.

Regarding the ink jet recording method, the method described inparagraphs “0093” to “0105” of JP2003-306623A can also be referred to.

Examples of ink jet heads used in the ink jet recording method includeink jet heads for a shuttle method of using short serial heads that arecaused to scan a base material in a width direction of the base materialso as to perform recording and ink jet heads for a line method of usingline heads that each consist of recording elements arranged for theentire area of each side of a base material.

In the line method, by causing the base material to be scanned in adirection intersecting with the arrangement direction of the recordingelements, a pattern can be formed on the entire surface of the basematerial. Therefore, this method does not require a transport systemsuch as a carriage that moves short heads for scanning.

Furthermore, in the line method, complicated scanning control for movinga carriage and a base material is not necessary, and only a basematerial moves. Therefore, the forming speed can be further increased inthe line method than in the shuttle method.

The amount of the first conductive ink jetted from the ink jet head ispreferably 1 pL (picoliter) to 100 pL, more preferably 3 μL to 80 pL,and even more preferably 3 pL to 20 pL.

In the first applying step, at the time of applying the first conductiveink, the temperature of the base material is preferably 20° C. to 120°C., and more preferably 40° C. to 80° C. In a case where the temperatureof the base material is 20° C. to 120° C., the influence of basematerial deformation or the like caused by heat is small, and drying ofthe ink is facilitated.

(First Baking Step)

The first baking step is a step of baking the first conductive ink.

In the first baking step, the baking temperature is preferably 250° C.or lower, and the baking time is 1 minute to 120 minutes.

The baking temperature is preferably 50° C. to 200° C., and morepreferably 60° C. to 120° C. The baking time is preferably 1 minute to40 minutes. In a case where the baking temperature and the baking timeare in the above ranges, it is possible to bake the ink while reducingthe influence of base material deformation or the like caused by heat.

The void ratio of the conductive ink film can be adjusted by the bakingtemperature and the baking time. For example, the higher the bakingtemperature is, the lower the void ratio tends to be.

The baking method is not particularly limited, and a generally knownmethod can be used.

The time from when the second applying step has finished to when thesecond baking step is started is preferably 60 seconds or less. Thelower limit of the time is not particularly limited, and is, forexample, 1 μs. In a case where the time is 60 seconds or less, beforethe conductive ink permeates the base material, the solvent contained inthe conductive ink is removed. As a result, a film having a higherdensity is likely to be formed on the surface of the conductive inkfilm.

“When the second applying step has finished” means a point in time whenall the droplets of the second conductive ink are landed on the basematerial.

“When the second baking step is started” refers to a point in time whenthe base material is placed in the device for the baking step and startsto be heated.

(Second Applying Step)

The second applying step is a step of applying a second conductive inkcontaining a metal complex onto the baked first conductive ink.

The method of applying the second conductive ink onto the baked firstconductive ink is not particularly limited, and examples thereof includeknown methods such as a coating method, an ink jet recording method, anda dipping method. Among these, from the viewpoint of making it possibleto form a thin conductive ink film by applying once a small amount ofthe conductive ink by means of jetting, it is preferable that the secondconductive ink be applied using an ink jet recording method in thesecond applying step. Details of the ink jet recording method are asdescribed above.

In the second applying step, at the time of applying the secondconductive ink, the temperature of the base material is preferably 20°C. to 120° C., and more preferably 40° C. to 80° C.

(Second Baking Step)

The second baking step is a step of baking the second conductive ink.

In the second baking step, the baking temperature is preferably 250° C.or lower, and the baking time is 1 minute to 120 minutes. In a casewhere the baking temperature and the baking time are in the aboveranges, it is possible to bake the ink while reducing the influence ofbase material deformation or the like caused by heat.

The baking temperature is preferably 50° C. to 200° C., and morepreferably 60° C. to 120° C. The baking time is preferably 1 minute to40 minutes.

The baking method is not particularly limited, and a generally knownmethod can be used.

EXAMPLES

Hereinafter, the present disclosure will be more specifically describedbased on examples, but the present disclosure is not limited to thefollowing examples as long as the gist of the present disclosure ismaintained.

<Preparation of conductive ink (silver particle ink)>

(1) Silver Particle Ink A1

—Preparation of Silver Particle Dispersion Liquid 1—

As a dispersant, 6.8 g of polyvinylpyrrolidone (weight-average molecularweight 3,000, manufactured by Sigma-Aldrich Corporation) was dissolvedin 100 mL of water, thereby preparing a solution a. In addition, 50.00 gof silver nitrate was dissolved in 200 mL of water, thereby preparing asolution b. The solution a and the solution b were mixed together andstirred, thereby obtaining a mixed solution. At room temperature, 78.71g of an 85% by mass aqueous N,N-diethylhydroxylamine solution was addeddropwise to the mixed solution. In addition, a solution obtained bydissolving 6.8 g of polyvinylpyrrolidone in 1,000 mL of water was slowlyadded dropwise to the mixed solution at room temperature. The obtainedsuspension was passed through an ultrafiltration unit (Vivaflow 50manufactured by Sartorius Stedim Biotech GmbH., molecular weightcut-off: 100,000, number of units: 4) and purified by being passedthrough purified water until about 5 L of exudate is discharged from theultrafiltration unit. The supply of purified water was stopped, followedby concentration, thereby obtaining 30 g of a silver particle dispersionliquid 1. The content of solids in this dispersion is 50% by mass. Thecontent of silver in the solids that was measured by TG-DTA(simultaneous measurement of thermogravimetry and differential thermalanalysis) (manufactured by Hitachi High-Tech Corporation, model: STA7000series) was 96.0% by mass. The obtained silver particle dispersionliquid 1 was 20× diluted with deionized water, and measured using aparticle size analyzer FPAR-1000 (manufactured by Otsuka ElectronicsCo., Ltd) to determine the volume-average particle diameter of thesilver particles. The volume-average particle diameter of the silverparticle dispersion liquid 1 was 60 nm.

—Preparation of Silver Particle Ink A1—

2-Propanol (2 g) and 0.1 g of OLFINE E-1010 (manufactured by NissinChemical Industry Co., Ltd.) as a surfactant were added to 10 g of thesilver particle dispersion liquid, and water was added thereto such thatthe silver concentration reaches 40% by mass, thereby obtaining a silverparticle ink A1.

(2) Silver Particle Ink A2

—Preparation of Silver Particle Dispersion Liquid 2—

Silver particle dispersion liquid 2 was prepared by the same method asthe silver particle dispersion liquid 1, except that the dispersant inthe silver particle dispersion liquid 1 was changed topolyvinylpyrrolidone (weight-average molecular weight 6,000,manufactured by Sigma-Aldrich Corporation), and the amount ofpolyvinylpyrrolidone added was changed to 7.4 g from 6.8 g. Thevolume-average particle diameter of the silver particle dispersionliquid 2 was 100 nm.

—Preparation of Silver Particle Ink A2—

A silver particle ink A2 was prepared by the same method as the silverparticle ink A1, except that the silver particle dispersion liquid 2 wasused instead of the silver particle dispersion liquid 1.

<Preparation of Conductive Ink (Silver Complex Ink)>

(1) Silver Complex Ink B1

1-Propanol (5.0 g), 0.17 g of silver acetate, and 0.05 g of formic acidwere added to a 50 mL three-neck flask, and the mixture was stirred for20 minutes. The generated silver salt precipitate was decanted 3 timesby using 1-propanol and washed. 1-Propylamine (0.12 g) and 5.0 g of1-propanol were added to the precipitate, and the mixture was stirredfor 30 minutes. Then, 1.0 g of water was added thereto, and the mixturewas further stirred, thereby obtaining a solution containing a silvercomplex. This solution was filtered using a membrane filter made ofpolytetrafluoroethylene (PTFE) having a pore diameter of 0.45 μm,thereby obtaining a silver complex ink B1.

(2) Silver Complex Ink B2

Isobutylammonium carbonate (6.08 g) and 15.0 g of isopropyl alcohol wereadded to a 50 mL three-neck flask, and dissolved. Then, 2.0 g of silveroxide was added thereto and reacted at normal temperature for 2 hours,thereby obtaining a homogeneous solution. Furthermore, 0.3 g of2-hydroxy-2-methylpropylamine was added thereto and stirred, therebyobtaining a solution containing a silver complex. This solution wasfiltered using a membrane filter made of polytetrafluoroethylene (PTFE)having a pore diameter of 0.45 μm, thereby obtaining a silver complexink B2.

(3) Silver Complex Ink B3

Silver neodecanoate (2.5 g), 5 g of xylene, and 3.0 g of terpineol wereadded to a 25 mL three-neck flask, and dissolved. Then, 1 g oftert-octylamine was added thereto and stirred, thereby obtaining asolution containing a silver complex. The reaction was carried out atnormal temperature for 2 hours, thereby obtaining a homogeneoussolution. This solution was filtered using a membrane filter made ofpolytetrafluoroethylene (PTFE) having a pore diameter of 0.45 therebyobtaining a silver complex ink B3.

(4) Silver Complex Ink B4

Water (5.0 g), 1.0 g of silver acetate, 1.0 g of ethylenediamine, and1.0 g of amylamine were added to a 25 mL three-neck flask, and themixture was stirred for 20 minutes. Formic acid (0.2 g) was added to theobtained solution, and the mixture was further stirred for 30 minutes,thereby obtaining a solution containing a silver complex. This solutionwas filtered using a membrane filter made of polytetrafluoroethylene(PTFE) having a pore diameter of 0.45 thereby obtaining a silver complexink B4.

<Preparation of Conductive Ink (Silver Salt Ink)>

Silver Salt Ink C1

Silver neodecanoate (4 g) was added to a 50 mL three-neck flask. Then,3.0 g of trimethylbenzene and 3.0 g of terpineol were added thereto andstirred, thereby obtaining a solution containing a silver salt. Thissolution was filtered using a membrane filter made ofpolytetrafluoroethylene (PTFE) having a pore diameter of 0.45 therebyobtaining a silver salt ink C1.

Example 1

As a base material, a polyethylene terephthalate film (trade name“Viewful UV TP-100”, manufactured by KIMOTO) was prepared. The inkcartridge (for 10 picoliters) for an ink jet recording device (tradename “DMP-2850”, manufactured by Fujifilm Dimatix Inc) was filled withthe silver particle ink A1. As image recording conditions, theresolution was set to 600 dots per inch (dpi), and the jetting amountwas set to 10 picoliters/dot. The base material was preheated to 60° C.,and a solid image having a width of 5 cm and a length of 10 cm wasrecorded on the base material at 60° C. (applying step 1). After a lapseof 1 second from when the last ink droplet of the silver particle ink A1was landed on the base material, the solid image was heated at 150° C.for 20 minutes by using a hot plate (baking step 1). In this way, aconductive ink film having metallic gloss was formed on the basematerial.

Then, the ink cartridge (for 10 picoliters) for an ink jet recordingdevice (trade name “DMP-2850”, manufactured by Fujifilm Dimatix Inc) wasfilled with the silver complex ink B1. The base material on which theconductive ink film was formed of the silver particle ink A1 waspreheated to 60° C., and a solid image was recorded on the base materialat 60° C. under the same conditions as the image recording conditionsdescribed above such that this solid image overlapped the aforementionedsolid image (applying step 2). After a lapse of 1 second from when thelast ink droplet of the silver complex ink B1 was landed on the basematerial, the solid image was heated at 120° C. for 20 minutes by usinga hot plate. In this way, a conductive laminate was obtained in which aconductive ink film having metallic gloss and a thickness of 7 μm wasformed (baking step 2).

Examples 2 to 18 and Comparative Examples 1 to 6

Conductive laminates were obtained by the same method as in Example 1,except that in Examples 2 to 18 and Comparative Examples 1 to 6, thetype of conductive ink, the temperature of the base material, the bakingtemperature, and the baking time were changed to the conditionsdescribed in Tables 1 and 2. Each treatment was performed in the orderof the applying step 1, the baking step 1, the applying step 2, thebaking step 2, the applying step 3, the baking step 3, the applying step4, and the baking step 4. For the examples and comparative examples inwhich the treatment was completed in the baking step 2, “-” is marked inthe applying step 3 and the following steps in the tables. In thetables, the thickness (film thickness) of the conductive ink film ineach of the conductive laminates is also described.

In Comparative Example 6, the baking temperature in the baking step 1was low. Therefore, silver was not fully baked, and a black conductiveink film was formed on the base material.

Example 19

In Example 19, a conductive laminate was obtained by the same method asin Example 2, except that the time from when the second applying stephas finished to when the second baking step is started was changed to 60seconds.

By using the conductive laminate obtained in each of the examples andcomparative examples, the first void ratio and the second void ratiowere measured, and evaluation was performed regarding the surfaceresistivity and the thermal cycle stability. The measurement results andthe evaluation results are shown in the tables.

<Measurement of First Void Ratio and Second Void Ratio>

By using a microtome (trade name RM2255, manufactured by LeicaBiosystems Nussloch GmbH), the conductive laminate was cut in athickness direction of the conductive laminate, thereby obtaining across section. By using the obtained cross section and a scanningelectron microscope (trade name S-4700, manufactured by HitachiHigh-Tech Corporation.), a cross-sectional observation image wasobtained.

By using image software (“Adobe Photoshop” manufactured by AdobeSystems, Inc.), threshold values of the obtained cross-sectionalobservation image were adjusted to obtain a binary image including awhite region where a conductive substance is present and a black regionwhere voids are present. In the obtained image, the projection portionsat five upper points and the recess portions at five lower points on theside of the ink film surface were averaged, and the position obtained inthis way was adopted as an upper side. Furthermore, for the basematerial side of the ink film, the same calculation as above wasperformed, and the position obtained by the calculation was adopted as alower side. The space between the upper side and the lower side wasdivided into 10 equal parts, and a region from the lower side to the 5thpart was defined as a 50% region on the base material side, and a regionfrom the 9th part from the base material side to the upper region wasdefined as a 10% region on the non-base material side.

The first void ratio was calculated as a ratio of the area of the blackregion (void) to the total area of the 50% region on the base materialside in the cross-sectional observation image.

The second void ratio was calculated as a ratio of the area of the blackregion (void) to the total area of the 10% region on the non-basematerial side in the cross-sectional observation image.

<Evaluation of Surface Resistivity>

A printing pattern was formed such that the surface of the conductiveink film had a size of 5 cm×10 cm, thereby obtaining an evaluationsample.

For the conductive ink film in the evaluation sample, by using aresistivity meter (trade name “Loresta GP”, manufactured by MitsubishiChemical Analytech Co., Ltd.), the surface resistivity [Ω/square] wasmeasured at room temperature (23° C.) by a 4-terminal method. Theevaluation standard is as follows. The conductive layer ranked 2 orhigher is at a level having no problem for practical use.

5: The surface resistivity is less than 5 me/square. 4: The surfaceresistivity is 5 mΩ/square or more and less than 10 Ω/square. 3: Thesurface resistivity is 10 mΩ/square or more and less than 15 Ω/square.2: The surface resistivity is 15 mΩ/square or more and less than 20Ω/square. 1: The surface resistivity is 20 Ω/square or more.

<Evaluation of Thermal Cycle Stability>

A printing pattern was formed such that the surface of the conductiveink film had a size of 5 cm×10 cm, thereby obtaining an evaluationsample.

For the conductive ink film in the evaluation sample, by using aresistivity meter (trade name “Loresta GP”, manufactured by MitsubishiChemical Analytech Co., Ltd.), the volume resistivity was measured inadvance.

The evaluation sample was subjected to a thermal cycle test at 60° C.and −20° C. The test was programmed such that the evaluation samplecould be alternately heated and cooled for 2 hours at each temperature.The test was performed for 7 days. After the test ended, the surfaceresistivity of the conductive ink film in the evaluation sample wasmeasured. Based on the amount of change between the surface resistivitybefore the start of the test and the surface resistivity after the endof the test, the thermal cycle stability was evaluated. The evaluationstandard is as follows. It can be said that the smaller the amount ofchange in the surface resistivity, the better the thermal cyclestability. The conductive layer ranked 2 or higher is at a level havingno problem for practical use.

Amount of change=(surface resistivity after end of test)−(surfaceresistivity before start of test)

5: The amount of change is less than 1.5 Ω/square.

4: The amount of change is 1.5 Ω/square or more and less than 2.0Ω/square.

3: The amount of change is 2.0 Ω/square or more and less than 2.5Ω/square.

2: The amount of change is 2.5 Ω/square or more and less than 3.0Ω/square.

1: The amount of change is 3.0 Ω/square or more.

TABLE 1 Example Example Example Example Example Example Example ExampleExample Example 1 2 3 4 5 6 7 8 9 10 Applying Type of conductive A1 A1A2 A2 A1 A1 A2 A1 A2 A2 step 1 ink Temperature of 60 60 60 60 60 60 6060 60 60 base material (° C.) Baking Baking temperature 150 130 130 130130 130 130 130 130 130 step 1 (° C.) Baking time (min) 20 20 20 20 2020 20 20 20 20 Applying Type of conductive B1 B1 B1 A1 B1 C1 C1 C1 B2 A2step 2 ink Temperature of 60 60 60 60 60 60 50 40 30 60 base material (°C.) Baking Baking temperature 120 120 120 160 120 150 150 150 140 150step 2 (° C.) Baking time (min) 20 20 20 20 20 20 20 20 20 20 ApplyingType of conductive — — — — B1 C1 C1 — B2 — step 3 ink Temperature of — —— — 60 60 60 — 30 — base material (° C.) Baking Baking temperature — — —— 120 150 150 — 140 — step 3 (° C.) Baking time (min) — — — — 20 20 20 —20 — Applying Type of conductive C1 C1 — B2 — step 4 ink Temperature of— — — — — 60 60 — 30 — base material (° C.) Baking Baking temperature —— — — — 150 150 — 140 — step 4 (° C.) Baking time (min) — — — — — 20 20— 20 — Second void ratio (%) 10 10 10 25 6 4 4 7 25 30 First void ratio(%) 15 35 50 40 35 35 45 35 35 40 Film thickness (μm) 6.5 6.5 6.5 12 7 88 6.5 8 12 Evaluation Surface resistivity 4 4 5 3 4 5 5 5 3 3 Thermalcycle 2 5 2 4 4 5 2 5 4 4 stability

TABLE 2 Example Example Example Example Example Example Example Example11 12 13 14 15 16 17 18 Applying Type of B1 A1 A1 A1 A1 A1 A1 A1 step 1conductive ink Temperature of 60 60 130 60 60 60 60 60 base material (°C.) Baking Baking 120 120 150 260 150 150 130 130 step 1 temperature (°C.) Baking time 20 20 20 20 20 20 20 20 (min) Applying Type of B1 A1 B1B1 B1 B1 B3 B4 step 2 conductive ink Temperature of 60 60 60 60 130 6060 60 base material (° C.) Baking Baking 120 120 120 120 120 260 130 140step 2 temperature (° C.) Baking time 20 20 20 20 20 20 (min) ApplyingType of — A1 — — — — — — step 3 conductive ink Temperature of — 60 — — —— — — base material (° C.) Baking Baking — 120 — — — — — — step 3temperature (° C.) Baking time — 20 — — — — — — (min) Applying Type of —A1 — — — — — — step 4 conductive ink Temperature of — 60 — — — — — —base material (° C.) Baking Baking — 120 — — — — — — step 4 temperature(° C.) Baking time — 20 — — — — — — (min) Second void ratio (%) 4 5 1010 25 5 9 11 First void ratio (%) 15 35 45 15 35 20 36 35 Film thickness(μm) 2 20 6.5 6.5 6.5 6.5 6.5 6.5 Evaluation Surface 5 5 4 4 3 5 4 4resistivity Thermal cycle 2 5 3 2 4 3 5 5 stability

TABLE 3 Comparative Comparative Comparative Comparative ComparativeComparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Applying Type of A1 A2 A1 A1 B1 A1 step 1 conductive ink Temperature 6025 60 60 60 25 of base material (° C.) Baking Baking 300 200 150 120 120100 step 1 temperature (° C.) Baking time 20 20 20 20 20 10 (min)Applying Type of B1 A2 A2 — — B1 step 2 conductive ink Temperature 60 6060 — — 25 of base material (° C.) Baking Baking 120 130 130 — — 175 step2 temperature (° C.) Baking time 30 20 20 — — 60 (min) Second void ratio(%) 5 35 35 30 10 30 First void ratio (%) 9 55 25 30 10 30 Filmthickness (μm) 6.5 12 12 6 1 6.5 Evaluation Surface 5 1 1 1 5 1resistivity Thermal cycle 1 4 3 4 1 3 stability

TABLE 4 Example 2 Example 19 Applying step 1 Type of conductive ink A1A1 Temperature of base material (° C.) 60 60 Baking step 1 Bakingtemperature (° C.) 130 130 Baking time (min) 20 20 Applying step 2 Typeof conductive ink B1 B1 Temperature of base material (° C.) 60 60 Bakingstep 2 Lapse of time from applying step 2 (sec) 1 60 Baking temperature(° C.) 120 120 Baking time (min) 20 20 Second void ratio (%) 10 20 Firstvoid ratio (%) 35 35 Film thickness (μm) 6.5 6.5 Evaluation Surfaceresistivity 4 2 Thermal cycle stability 5 5

As shown in Tables 1 to 3, it has been found that in Examples 1 to 18,the surface resistivity is low, and the thermal cycle stability isexcellent, because Examples 1 to 18 comprise a base material and aconductive ink film provided on the base material, and in a case where asurface of the conductive ink film close to the base material is definedas a first main surface, and a surface of the conductive ink film farfrom the base material is defined as a second main surface, a first voidratio in a region that extends from the first main surface toward thesecond main surface to a position being away from the first main surfaceby a distance equivalent to 50% of a thickness of the conductive inkfilm is 15% to 50%, and a second void ratio in a region that extendsfrom a position being away from the second main surface toward the firstmain surface by a distance equivalent to 10% of the thickness of theconductive ink film to the second main surface is lower than the firstvoid ratio.

On the other hand, it has been found that in Comparative Examples 1 and5, the first void ratio is less than 15%, and the thermal cyclestability is poor.

It has been found that in Comparative Example 2, the first void ratio ishigher than 50%, and the surface resistivity is high.

It has been found that in Comparative Examples 3, 4, and 6, the secondvoid ratio is the same as or higher than the first void ratio, and thesurface resistivity is high.

It has been found that in Example 1, at the time of applying the firstconductive ink in the step of applying the first conductive ink, thetemperature of the base material is 20° C. to 120° C., and the thermalcycle stability of Example 1 is better than that of Example 13.

It has been found that in Example 1, in the step of baking the firstconductive ink, the baking temperature is 250° C. or lower and thebaking time is 1 minute to 120 minutes, and the thermal cycle stabilityof Example 1 is better than that of Example 14.

As shown in Table 4, it has been found that in Example 2, the time fromwhen the second applying step has finished to when the second bakingstep is started is 1 second, and the second void ratio and the surfaceresistivity of Example 2 are higher than those of Example 19 in whichthe aforementioned time is 60 seconds.

The entire disclosure of Japanese Patent Application No. 2020-165595,filed Sep. 30, 2020 is incorporated into the present specification byreference. In addition, all documents, patent applications, andtechnical standards described in the present specification areincorporated into the present specification by reference, as if each ofthe documents, the patent applications, and the technical standards isspecifically and individually described.

What is claimed is:
 1. A conductive laminate comprising: a basematerial; and a conductive ink film provided on the base material,wherein the conductive ink film has a first main surface and a secondmain surface, wherein the first main surface is closer to the basematerial than the second main surface and the second main surface isfarer from the base material than the first main surface, a region thatextends from the first main surface toward the second main surface to aposition being away from the first main surface by a distance equivalentto 50% of a thickness of the conductive ink film has a first void ratioof 15% to 50%, a region that extends from a position being away from thesecond main surface toward the first main surface by a distanceequivalent to 10% of the thickness of the conductive ink film to thesecond main surface has a second void ratio which is smaller than thefirst void ratio, and the conductive ink film comprises at least onemetal selected from the group consisting of silver, gold, platinum,nickel, palladium, and copper.
 2. The conductive laminate according toclaim 1, wherein the first void ratio is 30% to 40%.
 3. The conductivelaminate according to claim 1, wherein the second void ratio is 20% orless.
 4. The conductive laminate according to claim 1, wherein theconductive ink film has a thickness of 0.5 μm to 30 μm.
 5. A method ofmanufacturing the conductive laminate according to claim 1, the methodcomprising: applying a first conductive ink comprising metal particlesonto a base material; baking the first conductive ink; applying a secondconductive ink comprising a metal salt or a metal complex onto the bakedfirst conductive ink; and baking the second conductive ink.
 6. Themethod according to claim 5, wherein the metal particles are particlescomprising at least one metal selected from the group consisting ofsilver, gold, platinum, nickel, palladium, and copper.
 7. The methodaccording to claim 5, wherein the metal particles have an averageparticle diameter of 10 nm to 200 nm.
 8. The method according to claim5, wherein the first conductive ink has a content of the metal particlesof 10% by mass to 90% by mass with respect to a total amount of thefirst conductive ink.
 9. The method according to claim 5, wherein eachof the metal salt and the metal complex comprises at least one metalselected from the group consisting of silver, gold, platinum, nickel,palladium, and copper.
 10. The method according to claim 5, wherein themetal complex is a metal complex having a structure derived from atleast one compound selected from the group consisting of an ammoniumcarbamate compound, an ammonium carbonate compound, an alkylamine, and acarboxylic acid having 8 to 20 carbon atoms, and the metal salt is ametal carboxylate having 8 to 20 carbon atoms.
 11. The method accordingto claim 5, wherein the second conductive ink has a content of each ofthe metal salt and the metal complex of 10% by mass to 90% by mass withrespect to a total amount of the second conductive ink.
 12. The methodaccording to claim 5, wherein the applying of the first conductive inkcomprises applying the first conductive ink using an ink jet recordingmethod, and the applying of the second conductive ink comprises applyingthe second conductive ink using an ink jet recording method.
 13. Themethod according to claim 5, wherein at the time of applying the firstconductive ink in the applying of the first conductive ink, atemperature of the base material is 20° C. to 120° C.
 14. The methodaccording to claim 5, wherein in the baking of the first conductive ink,a baking temperature is 250° C. or lower, and a baking time is 1 minuteto 120 minutes.
 15. The method according to claim 5, wherein at the timeof applying the second conductive ink in the applying of the secondconductive ink, a temperature of the base material is 20° C. to 120° C.16. The method according to claim 5, wherein in the baking of the secondconductive ink, a baking temperature is 250° C. or lower, and a bakingtime is 1 minute to 120 minutes.
 17. The method according to claim 5,wherein a time from when the applying of the second conductive ink hasfinished to when the baking of the second conductive ink is started is60 seconds or less.